Industrial control systems are for instance applied in manufacturing and process industries, such as chemical plants, oil production or processing plants, refineries, pulp and paper mills, steel mills and automated factories. Industrial control systems are also widely used within the electrical power industry. Such industrial control systems have a large amount of network infrastructure, of which a major proportion can be based on Ethernet and TCP/IP technology. With such large data and control infrastructures there is an important requirement for an efficient supervision of the plant behaviour, and also for efficient supervision of the network infrastructure.